Enhancement: allow customizing TypedDict keys that are invalid identifiers

### Summary

With the [alternative syntax](https://typing.python.org/en/latest/spec/typeddict.html#alternative-syntax) for TypedDict it is possible to construct one with keys that cannot be represented using the class syntax due to variable naming issues. There does not seem to be any way in polyfactory to customize these fields.

```python
from typing import TypedDict, NotRequired
from polyfactory.factories.typed_dict_factory import TypedDictFactory

A = TypedDict("A", {"x": int, "y": NotRequired[str], "#not-valid-identifier": float})

class AFactory(TypedDictFactory[A]):
# Nothing can be done here to change the behavior for generating "#not-valid-identifier"
pass

print(AFactory.build()) # {'x': 544, 'y': 'egGRVOHCaCMUAwOchRWT', '#not-valid-identifier': 427363237424.216}
```

### Basic Example

_No response_

### Drawbacks and Impact

_No response_

### Unresolved questions

_No response_

Start in polyfactory/factories/typed_dict_factory.py at TypedDictFactory and trace how fields from the alternative TypedDict syntax are discovered and customized. Check the existing factory customization mechanisms, then verify that a custom value for "#not-valid-identifier" is used when building the TypedDict.

Written by the indexing model from the issue text.